1. Field of the Invention
The present invention relates to a hydraulic motor for driving a hydraulically driven fan system that is for use with any kind of machine having an internal combustion engine.
2. Discussion of the Related Art
A vane pump is disclosed in Japanese Patent Laid-Open No. 271,982/1987. This known pump is now described with reference to FIG. 6. The pump has a housing 3 and a cam ring 1. One end of the ring 1 is closed off by a rear plate 2 which seals the housing 3 as a rear cover. The rear plate 2 is provided with a bearing hole 4 in which the protruding end 7 of a drive shaft 6 is inserted. The shaft 6 extends through a rotor 5. The protruding end 7 is held in the hole 4 via a bearing 8. The rear cover 2 is provided with a pair of knock holes which are arranged symmetrically with respect to the center of the hole 4 and remote from this center. Knock pins 9 are mounted in the knock holes with a press fit.
FIG. 7 shows an oil pump and a water pump which are simultaneously driven in a single-shaft multicylinder internal combustion engine as proposed in Japanese Patent Publication No. 42329/1985. A gear pump for lubricating oil has driven teeth 10. A coolant pump 11 has blades 12. The teeth 10 and the blades 12 are mounted on a common pump shaft 13, which is mounted inside a pump casing 14 and a casing 15. An oil seal 16 and a mechanical seal 17 are disposed between the pump teeth 10 and the pump blades 12.
For the vane pump shown in FIG. 6, the rear plate 2 is mounted coaxially with the housing 3 by use of the two knock pins 9. Therefore, it is difficult to mount the bearing 18 coaxially with the bearing 8. Also, it is difficult to achieve smooth rotation.
In the internal combustion engine shown in FIG. 7 the lubricating oil pump and the cooling water pump are driven simultaneously. The pump blades 12 are mounted to the pump shaft 13 with a press fit and so the mechanical seal 17 and the oil seal 16 cannot be detached. This presents problems in maintaining the engine.